userChrome.css (Modified Version of Ahoka's)

/* HIDDEN ELEMENTS */
#identity-box,
#urlbar-icons > image,
#urlbar-container dropmarker,
#appmenu-toolbar-button .toolbarbutton-text,
#appmenu-toolbar-button .toolbarbutton-menu-dropmarker
{
    display:none!important;
}

/* BUTTONS */
#back-button .toolbarbutton-icon,
#forward-button .toolbarbutton-icon,
#reload-button .toolbarbutton-icon,
#urlbar-reload-button .toolbarbutton-icon,
#stop-button .toolbarbutton-icon,
#urlbar-stop-button .toolbarbutton-icon,
#tabbrowser-tabs tab .tab-close-button .toolbarbutton-icon,
#new-tab-button .toolbarbutton-icon,
#appmenu-toolbar-button .toolbarbutton-icon,
.findbar-closebutton
{
    list-style-image:url("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAEIAAAALCAYAAADLA1tMAAAAGXRFWHRTb2Z0d2FyZQBBZG9iZSBJbWFnZVJlYWR5ccllPAAAA5xJREFUeNrsVk1IG0EU3s3mx1RXY2qxaa0ULFakUogUESUnPaS0Wlo1oifbQ0AUDx704EGIeBAkUXOzEq0/kHpose2h2IbexUKLFA8VokIPKaghrfmpyfa9dELHcTai0FsXNpPZ+d43b9773tsVFUUR/l+CoM38EUWRXZPg1sCdgjuJDzJBI9gT61kukeyFNgrBJ8n/NC9waii+FGWr9vzUdcKb8VWifBVpG8RpVByXent7rywtLSX6+voKeAB8juuII5sIKk5qAZs/OzvrWVxc3Jufn38zPT39hASGjr5mYWEh0NTUVEDxSTgHuy+Ei5tMWP9IJ5W9enp6isDX+OTk5H3CfcKGR64dGhq6UVtbu7OxsXFzYmIizCPH57iOOMRzHNE0NzcXwsE/GAyGYgjE4MrKyrWDgwOvTqezQTAeMwFMra+vO9rb27/bbDYZ5rq6urpch8OxOzMzc0dFDZlsl2VJhuD1eiM4ms1mNySlGLlZGzYQksvlulVZWbm5trZ2fXR0dCuL7JO4jjjEox1NDGuXW1pa3oI0S6uqql5Fo9Ejv9+/Bwp6HYlElnNyclrZQLjd7tDY2JjZ6XRuw9zY3d39rbOz81IgEIhwykWPGLgNsEd6JHO9mnrC4bDParW6MRDE5m/t0nXf1dWV19jYGIHM3B4fH9+Exwm25jj9RN/f319RXV39aXV1Vfb5fD8yzjY0NBQBZxAcGITDvxgYGNhFc1BKUVtb2zYc0gzzGFXLAsmWEaQc7ujowDKJwv1LpRzKyIHEP+4piN0CXiuMRxTvBeD7CXxmUOjLUCj0zGKxPIV5Lqwdps+FP9SbQyJGcciGhZUbg03jEYd4tOPI0zA3N/fe4/E8pDKlnZqaegAOvSNZPLY/9IRCOCSWYz7wHoGUr3J4aUWYAIdqMbGKoHiNBJOHZQx7f4W5QnwWeM0SyyAGkTLV19cHQe4VWWoPy6gCcYhHO04ZJROJxHOTyfQIDn8XlHARxnuyLLfGYrFlBq+x2+0y9IQg9IRSVAKWSU1Nzfbw8DDrR4qoFRUQJ0qIk3mC108IJjkyMhLc3993CRyAwPmWwAAZscsTqfKwOrJuzNLRUZc6aIxOVADgD3HEOeEVqcyl5Q4dvph+a5SXl8uojJKSEr3KHnqw+0yUIPBKmcGIRCEKrUhRpe6572cGe9r7nQ5G5j0unvM7QiL4835HsJhjnLwekfU6C/Ys17/6uj3LuX4LMACwT+lvQQrZSgAAAABJRU5ErkJggg==")!important;
}
#back-button .toolbarbutton-icon
{
    -moz-image-region:rect(0, 11px, 11px, 0)!important;
}
#forward-button .toolbarbutton-icon
{
    -moz-image-region:rect(0, 22px, 11px, 11px)!important;
}
#reload-button .toolbarbutton-icon,
#urlbar-reload-button .toolbarbutton-icon
{
    -moz-image-region:rect(0, 33px, 11px, 22px)!important;
}
#stop-button .toolbarbutton-icon,
#urlbar-stop-button .toolbarbutton-icon,
#tabbrowser-tabs tab .tab-close-button .toolbarbutton-icon,
.findbar-closebutton
{
    -moz-image-region:rect(0, 44px, 11px, 33px)!important;
}
#new-tab-button .toolbarbutton-icon
{
    -moz-image-region:rect(0, 55px, 11px, 44px)!important;
}
#new-tab-button
{
    max-width:16px!important;
}
#appmenu-toolbar-button .toolbarbutton-icon
{
    -moz-image-region:rect(0, 66px, 11px, 55px)!important;
}
#main-window toolbarbutton,
.tab-close-button,
.findbar-closebutton,
#appmenu-toolbar-button
{
    background:transparent!important;
    border:0!important;
    min-height:18px!important;
    max-height:18px!important;
    min-width:14px!important;
    max-width:14px!important;
    padding:0!important;
    -moz-appearance:none!important;
}
#main-window toolbarbutton,
#appmenu-toolbar-button
{
    padding-top:2px!important;
}
.findbar-closebutton
{
    margin:-1px 0 0 5px!important;
}

/* URL BAR */
#urlbar
{
    background:#161616!important;
    border:0!important;
    color:rgba(255,255,255,.6)!important;
    margin:2px 0 0!important;
    max-height:18px!important;
    min-height:18px!important;
    padding:0!important;
    text-align:left!important;
    text-shadow:rgba(0,0,0,.6) 0 0 1px!important;
    -moz-transition:color .2s ease-in-out;
    -moz-appearance:none!important;
}
#urlbar:hover
{
    color:rgba(255,255,255,.8)!important;
}
#urlbar #notification-popup-box
{
    background:-moz-linear-gradient(rgba(75,75,75,.2),rgba(0,0,0,.4))!important;
    border-right:1px solid rgba(0,0,0,.4)!important;
    max-height:16px!important;
    max-width:16px!important;
    padding:0 4px!important;
    border-radius:1px 0 0 1px!important;
    -moz-border-image:none!important;
    -moz-margin-end:0!important;
}
#urlbar #notification-popup-box .notification-anchor-icon
{
    max-height:10px!important;
    max-width:10px!important;
}

/* TABS */
#main-window #tabbrowser-tabs tab
{
    background:#1c1c1c!important;
    border:0!important;
    border-left:0 solid #101010!important;
    border-right:1px solid #101010!important;
    color:rgba(255,255,255,.6)!important;
    text-shadow:rgba(0,0,0,.8) 0 0 1px!important;
}
#main-window #tabbrowser-tabs tab:first-child
{
    border-left:1px solid #101010!important;
}
#main-window #tabbrowser-tabs tab
{
    margin:3px 0 -3px!important;
    max-height:16px!important;
    min-height:16px!important;
    padding:0 2px!important;
    border-radius:0!important;
}
#main-window #tabbrowser-tabs tab[selected]
{
    color:#fff!important;
}
#main-window #tabbrowser-tabs tab .tab-throbber,
#main-window #tabbrowser-tabs tab .tab-icon-image
{
    max-height:10px!important;
    max-width:10px!important;
    margin-top:0px!important;
}
#main-window #tabbrowser-tabs tab[fadein]
{
    -moz-transition:all .2s ease-in-out!important;
}
#main-window #tabbrowser-tabs tab:not([selected]):hover
{
    color:rgba(255,255,255,.8)!important;
}
#main-window #tabbrowser-tabs tab .tab-close-button
{
    min-height:16px!important;
    max-height:16px!important;
    opacity:0!important;
    -moz-transition:all .1s ease-in-out!important;
}
#main-window #tabbrowser-tabs tab .tab-close-button .toolbarbutton-icon
{
    max-height:7px!important;
    max-width:7px!important;
}
#main-window #tabbrowser-tabs tab[selected] .tab-close-button,
#main-window #tabbrowser-tabs tab:hover .tab-close-button
{
    opacity:1!important;
}
#main-window #tabbrowser-tabs tab[fadein]:not([pinned])
{
    min-width:40px!important;
    max-width:160px!important;
}
#main-window #tabbrowser-tabs tab[pinned]
{
    max-width:24px!important;
    min-width:24px!important;
}
#main-window #tabbrowser-tabs tab[pinned] .tab-close-button
{
    display:none!important;
}

/* MAIN WINDOW */
#main-window #urlbar,
#main-window #urlbar-container
{
    max-width:240px!important;
}
#main-window:not([chromehidden*="toolbar"])
{
    margin:0!important;
}
#main-window #TabsToolbar
{
    background:#161616!important;
    border-bottom:1px solid #101010!important;
    max-height:20px!important;
    min-height:20px!important;
    margin:-3px 0 0!important;
    padding:0 2px 0 0!important;
}
#main-window #appmenu-toolbar-button
{
    background:transparent!important;
    border:0!important;
    padding-left:6px!important;
    box-shadow:none!important;
}
#main-window #appmenu-toolbar-button
{
    margin:0!important;
}

scrollbar,
scrollcorner
{
    background:#161616!important;
    -moz-appearance:none!important;
}
thumb
{
    border:0!important;
    background:#222222!important;
    -moz-appearance:none!important;
}
thumb:active,
thumb:hover
{
    background:#1b1b1b!important;
    -moz-appearance:none!important;
}

select > button,
select > input
{
    opacity:0!important;
}